In the last few years the use of wireless technologies has been very prevalent, in particular wireless cellular telephones. Cellular telephones deploy various types of radio frequency baseband and base station modern protocols such as Code Division Multiple Access (CDMA), Global Systems for Mobile Communication (GSM), General Pocket Radio Services (GPRS), (PDC) etc.
In general, a cellular telephone has a baseband chip which provides the computing needs for voice communications. This baseband chip usually includes a Central Processing Unit (CPU), a memory interface for interfacing non-volatile (FLASH type memories) or volatile Pseudo Static Random Memory (pSRAM), Static Random Access Memory (SRAM), Synchronous Dynamic Random Access Memory (SDRAM) type memories) memories, a Liquid Crystal Display (LCD) controller, keyboard and audio devices or interfaces to, and a mechanism to interface Radio Frequency (RF) components to establish a link to a base station.
Until recently, cellular telephones were used for voice only communications only, but with the Internet, various wireless carriers such as SKT, J-Phone, DoCoMo, Verizon, Vodaphone etc. have sought to provide data services to cellular telephone users in order to realize higher revenues per subscriber.
Such data services generally require a higher performance from the baseband chips. In some cases, in order to reduce the performance demands on the baseband chips, an application chip may also be provided to execute specific applications. The application chip and the baseband chip generally require a memory sub-system.
The memory sub-system of the cellular telephone, represents one of the highest cost components of the cellular telephone, and thus the manner in which access to the memory sub-system by the baseband chip and the application processor can have a significant effect on the cost and performance of the cellular telephone.